My concern would be the 17.4 psi limitation. Standard air pressure is 14.7 psi. At a depth of 10 feet, the water pressure is 1.3 atmospheres, or about 19.1 psi. So this compressor cannot even pump air down 10 feet underwater, let alone get enough volume down to a diver that deep.

And then, is the flow rating at the full 17.4 or is that "free flow." A lot of compressors, in order to "pump up" their numbers, will list free flow volume and maximum psi, and not mention that at maximum psi the flow is going to be WAAAAY less.

Edit:

Oops! Just realized that my math is wrong. I was including the 1 atmosphere of pressure that we start with at sea level. So, if this thing can pump 17.4 psi then it can pump air down almost 40 feet. The question remains, though, if it will actually deliver the full flow at that depth.

And then, most of the regulators that I've seen that are made for hookah diving are adjusted to work with 40-60 psi of delivered air pressure. "Normal" scuba regulators work with around 100 psi of delivered air pressure. Obviously, these regulators would not work with that compressor, which may be why the ebay sellers plumb it to a snorkel, instead of a real regulator.

...which may be why the ebay sellers plumb it to a snorkel, instead of a real regulator.

I guarantee that's the reason. And since there is no regulator, excess air (assuming there is any) must be continuously exhausted. If you ever dived with a regulator that was "free-flowing", you know what a PITA this is.

Wow, now we really have the (inappropriate language for a sailing thread removed by tdw) : 40 feet on a McGuivered Wallmart Hooka! Ouch!

For anyone considering such a thing: DON'T.

When I was saying the el cheap hookah might work, I meant FOR SHALLOW HULL WORK.
Less than 12 feet, depths that one can easily surface from if the thing stops.

Someone who is looking at 40 feet+ dives, should really heed ALL the safety advice given by others earlier in the thread.
Get certified, or at least read and understand the book.
Understand dive times.
Get reasonably fail safe equipment.

etc.

[and girls: the current post BELONGS above the quoted text.
That's how it is done.
Reason is that one re-reads the quoted text only when he has to.
Like you two should have. ]

My concern would be the 17.4 psi limitation. Standard air pressure is 14.7 psi. At a depth of 10 feet, the water pressure is 1.3 atmospheres, or about 19.1 psi. So this compressor cannot even pump air down 10 feet underwater, let alone get enough volume down to a diver that deep.

And then, is the flow rating at the full 17.4 or is that "free flow." A lot of compressors, in order to "pump up" their numbers, will list free flow volume and maximum psi, and not mention that at maximum psi the flow is going to be WAAAAY less.

Edit:

Oops! Just realized that my math is wrong. I was including the 1 atmosphere of pressure that we start with at sea level. So, if this thing can pump 17.4 psi then it can pump air down almost 40 feet. The question remains, though, if it will actually deliver the full flow at that depth.

And then, most of the regulators that I've seen that are made for hookah diving are adjusted to work with 40-60 psi of delivered air pressure. "Normal" scuba regulators work with around 100 psi of delivered air pressure. Obviously, these regulators would not work with that compressor, which may be why the ebay sellers plumb it to a snorkel, instead of a real regulator.

THE MATH BEHIND OPEN END SYSTEMS
One way to measure the volume is how long it takes to empty an inverted container, corrected for a pressure of 15 psi,
the pressure at 32 feet deep, above atmospheric pressure at the surface of the water. One foot of water is about 1/2
psi.(Actually, it's closer to 14.7/32=0.459 psi per foot of water depth)
The absolute pressure(Pabs.) would be:
Pabs=14.7(sea level) + 1/2d, where d=the depth of water to the discharge depth
of the compressor hose.
Using:
(P1)(V1)(T1)=(P2)(V2)(T2) (gas law), where pis pressure, V is volume and T is temperature
in degrees absolute.
V2=(P1)(V1)/(P2) where T1=T2 and the pressures are absolute pressures.
Let P2=pressure of water at the discharge depth, and let P1 = 14.7
P2= (14.7 + 0.459d), so the equation becomes:
V=(14.7)(V1)/(14.7 + 0.459d)
So, if your compressor produces 200 cuft/hr at the surface, at a depth of 20 feet,
it will produce:
V(@20 ft)=(14.7)(200)/(14.7 + 0.459 x 20)
=2940/(14-7 + 9.18)
=2940/23.88
=120(approx) cuft.
If there is any heating of the air, during compression and subsequent cooling
of the air, in the diver's supply line, then temperature must be taken into
consideration and the T2 = the discharge air temperature (measured) and
T1=exit air from the compressor output port. I don't think that the difference
is too significant to the calculation, pressures are the overriding
factors, since on the absolute temperature scale (459 degrees Absolute, Rankine,
= zero Fahrenheit, so (example) 60 degrees F =519 degrees R).
The minimum needed at 32 feet is 100-120 cuft/hour, but 150-180 cufh would
BE SAFER.

I simply said that the compressor was capable of pushing air down 40 feet. I did not recommend that it be used at that depth. I didn't even come close to IMPLYING that it could be used at that depth. In fact, I specifically expressed my doubts about its ability to supply adequate air at that depth.

But I guess calling people names is a lot easier than actually reading what they are saying, and responding on topic to the thread.

By choosing to post the reply above you agree to the rules you agreed to when joining Sailnet.
Click Here to view those rules.

Register Now

In order to be able to post messages on the SailNet Community forums, you must first register. Please enter your desired user name, your email address and other required details in the form below.Please note: After entering 3 characters a list of Usernames already in use will appear and the list will disappear once a valid Username is entered.

User Name:

Password

Please enter a password for your user account. Note that passwords are case-sensitive.

Password:

Confirm Password:

Email Address

Please enter a valid email address for yourself.

Email Address:

OR

Log-in

User Name

Password

Remember Me?

Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.